Method and apparatus for resin delivery with adjustable air flow limiter

ABSTRACT

Method and apparatus for air flow limiting comprise a vertically oriented tube, a sail assembly positioned in the tube and moveable therewithin responsively to air flow through the tube to limit rate of air flow through the tube and halt air flow through the tube upon air flow rate through the tube exceeding a preselected value, and a moveable stop for adjustably changing the length of travel of the sail assembly thereby changing the maximum amount of air flow.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a 35 USC 120 continuation-in-part of U.S.Ser. No. 14/185,016 entitled “Air Flow Regulator” filed 20 Feb. 2014 inthe name of Stephen B. Maguire, and is also a 35 USC 120continuation-in-part of U.S. Ser. No. 14/574,561 entitled “ResinDelivery System with Air Flow Regulator” filed 18 Dec. 2014 in the nameof Stephen B. Maguire, and is further a 35 USC 120 continuation-in-partof U.S. Ser. No. 14/593,010 entitled “Air Flow Limiter With Closed/OpenSensing” filed 9 Jan. 2015 in the name of Stephen B. Maguire. Applicantclaims the priority of all of these pending utility patent applicationsas well as the priority, under 35 USC 119 and 120, of provisional U.S.patent application 62/027,379 filed 22 Jul. 2014 in the name of StephenB. Maguire, entitled “Central Vacuum Loading System Without CentralControl”.

TECHNOLOGICAL BACKGROUND

This invention relates to manufacture of plastic articles and moreparticularly relates to pneumatic conveyance and processing of plasticresin pellets prior to molding or extrusion of those pellets into afinished or semi-finished plastic product.

In this patent application, injection and compression molding pressesand extruders are collectively referred to as “process machines.”

The plastics industry is very diversified; there are thousands ofdifferent products, hundreds of materials, and dozens of processes, andall are very different from one another. The only thing all thesedifferences share in common is that the source material is some type ofplastic.

Equipment sold to this industry is, therefore, very diversified indesign. Plastics factories have multiple process machines, sometimesseveral hundred in one location. Virtually all plastics fabricatingoperations require that each process machine, namely a molding press oran extruder, be supplied automatically with the required raw resinmaterial on a continuous basis. This resin may be supplied in largeboxes, called Gaylords, in fiber drums, in 50 pound bags, or moretypically may be delivered by bulk truck or rail car, with the resinmaterial then being transferred in bulk into storage silos. In all casesthe resin material must be further distributed throughout the plant toeach and every process machine. For that reason a great deal of designand capital expense is devoted to the automatic distribution of the rawresin material throughout the plant.

These resin distribution systems, more commonly referred to as “LoadingSystems”, must deal with many variables. One set of variables includesthe type, shape, size and consistency of the granular material.

Resin pellets, nominally about ⅛ inch in size, come in various shapes,with round, square, and cylindrical being the most common.

Flowing resin powder is also an option, and very fine but free flowingresin pellets and other granular materials may be conveyed as well.

The design variables to be considered for each customer include:

-   -   1. Type of resin being conveyed.    -   2. Size and consistency of the resin pellets.    -   3. Distances the resin pellets are to be conveyed.    -   4. Variability of these distances from shortest to longest.    -   5. Acceptable range for velocity of resin material travel        through the lines.    -   6. Throughput rate of resin required for each machine.    -   7. Total throughput rate of resin for the entire plant.    -   8. Excess capacity performance margin so a molding or extrusion        process is not interrupted by short term loading issues.    -   9. Loss of resin material from or at the supply so that only air        is being pulled, thereby reducing system vacuum levels and        reducing overall design throughput.    -   10. Loading sequence, or priority, when multiple receiver        stations call for material.    -   11. Detecting problems and alarm conditions.    -   12. Proper air to material ratio for resin conveying.    -   13. Detecting plugged lines due to poor resin flow or over        feeding of resin material.    -   14. Dust condition and filter requirements.    -   15. Reliability.    -   16. Serviceability.    -   17. Ease of use.    -   18. Cost    -   19. Vacuum pump type, namely positive displacement,        regenerative, and others.    -   20. Vacuum pump horsepower and rated CFM capacity as well as        vacuum levels.

In all of these areas, system designers look to find improved methodsand solutions whenever possible.

One of the most important considerations is to hold a correct velocityfor the conveyed resin material. The type of resin material dictates thetarget conveying speed. To maximize the resin material transfer rate, ahigh conveying speed is preferred, and air speed in any case must besufficient to keep the resin pellets suspended and moving in the airstream. But velocity must be limited so as not to damage the pellets.Hard brittle pellets can fracture and break when conveyed, resulting inexcessive dust.

Softer pellets can skid along the conduit walls, causing “angel hair” asa result of the plastic resin melting at the point of high speed contactwith the conduit wall; this leaves a thin film on the wall. Strings ofvery thin “angel hair” accumulate, effectively reducing diameter of theconduit and causing problems in the system.

Air speed and resin conveying velocity are directly related to pumpcapacity (rated CFM) and horsepower, as well as conveying line diameter.There is always a correct velocity “range” for each type of resinmaterial. It is a design challenge to assure that resin material isconveyed within the correct velocity range.

Conveying distances affect system design. Conveying over short distancesrequires a less powerful vacuum source then over longer distances.Systems are generally sized to produce the best compromise for materialvelocity between the shortest and longest conveying distance.

Required conveying rate usually dictates line size (tube diameter), andthis in turn dictates the CFM required to maintain correct velocity in agiven diameter conduit. This means different tube sizes in the samesystem can be a problem if one vacuum pump is to draw air and resinthrough several different diameter conveying lines. Pumps have known CFMratings. Pulling air through a small tube will result in higher velocityflow than pulling the same CFM through a larger tube.

Excessive velocity can damage pellets.

The type of vacuum pump to be selected is important. Regenerativeblowers deliver wide ranging CFM depending on vacuum level. Positivedisplacement type pumps deliver high vacuum levels, and have a flatterCFM curve over their vacuum range. Regenerative blowers are quieter andgenerally cost less. Positive displacement blowers may require soundenclosures and tend to cost more, but are generally more reliable andmore forgiving as respecting dust in the air.

The simplest systems use a fixed speed motor to drive the vacuum pump,and a single size conveying line to serve all receivers regardless ofdistance, rate requirement, or material.

BACKGROUND OF THE INVENTION Description of the Prior Art

Current resin central loading systems concerned with conveying granularplastic resin pellets from a storage area for molding or extrusiontypically include a vacuum pump or pumps and multiple receivers.

In some systems, with many receivers, several small pumps are used.

It would be less expensive to use only one, or fewer, larger pumps.However, a larger pump may draw too much air with resulting damage tothe material being conveyed. While a larger pump could load severalreceivers at once, there is a risk that an “open” line, namely a linepulling only air, and no resin material, would cause the vacuum to droptoo much, and no resin would load. Also, when only one receiver isloading resin, air velocity might be too high, again with a risk ofdamaging the resin.

Nevertheless, in facilities that fabricate plastic products by moldingor extrusion, it is common to use such vacuum loading systems topneumatically convey pellets of thermoplastic resin, prior to molding orextrusion of those pellets into a finished or semi-finished product. Theplastic resin pellets are typically purchased in 50 pound bags, 200pound drums, or 1,000 pound containers commonly referred to as“Gaylords.”

A preferred approach for conveying plastic resin pellets from a storagelocation to a process machine, which approach is often used in largerfacilities, is to install a central vacuum pump or even several vacuumpumps, connected by common vacuum lines to multiple “receivers.”

Vacuum pumps connected to the vacuum lines draw vacuum, namely air atpressure slightly below atmospheric, as the vacuum pump sucks airthrough the “vacuum” line. The suction moves large quantities of airwhich carries thermoplastic resin pellets through the “vacuum” line.

An alternative is to use positive pressure produced by a blower or theexhaust side of a vacuum pump. With such an approach, the positivepressure results in movement of substantial amounts of air which may beused to carry the plastic resin pellets. However, the vacuum approach ofdrawing or sucking pellets through the system conduits is preferable tothe positive pressure approach of pushing the resin pellets through thesystem conduits.

In practice, vacuum pumps are preferred and vacuum lines are desirablein part because power requirements to create the required vacuumnecessary to draw plastic resin pellets through the lines are lower thanthe power requirements if the plastic resin pellets are pushed throughthe lines by a blower or by the exhaust side of a vacuum pump. Whenvacuum is used, the static pressure within the line may be not much lessthan atmospheric. When positive pressure is used, the dynamic pressureof the air flowing through the line must be relatively high in order tomove an adequate quantity of plastic resin pellets.

As used herein, and in light of the foregoing explanation, the terms“vacuum pump” and “blower” are used interchangeably.

When one or more central vacuum pumps are connected to multiplereceivers, a receiver is typically located over each temporary storagehopper, in which the plastic resin pellets are temporarily stored beforebeing molded or extruded. A temporary storage hopper is typicallyassociated with each process machine.

In current practice, the receiver is connected by a control wire to acentral control system. The control system works by selectively openinga vacuum valve located in each receiver, allowing one or several vacuumpumps to work in sequence drawing “vacuum”, i.e. below atmosphericpressure air, to carry the pellets among and to multiple receivers asindividual ones of the receivers, positioned over individual hoppersassociated with the individual process machines, require additionalplastic resin pellets. The receiver for a given hopper-process machinecombination is actuated by opening the vacuum valve located in or nearthe receiver, causing the receiver to supply plastic resin pellets bygravity feed into the hopper from where the pellets may be fed furtherby gravity downwardly into the associated process machine.

Large, high capacity industrial vacuum pumps are reliable and are suitedto heavy duty industrial use. Large high capacity vacuum pumps allowlong conveying distances for the plastic resin pellets. Currentlyavailable large capacity vacuum pumps permit plastic resin pellets to beconveyed over distances of 200 feet or more using vacuum drawn by thepump. Use of such high capacity vacuum pumps results in a big rush ofbelow atmospheric pressure air through the line, carrying the plasticresin pellets over a long distance.

Operators of plastic manufacturing facilities prefer to buy plasticresin pellets in bulk, in rail cars or tanker trucks. Bulk purchasesresult in cost savings. Plastic resin pellets delivered in bulk aretypically pumped into large silos for storage. In a large manufacturingfacility, the distance from a plastic resin pellet storage silo to aprocess machine may be several hundred feet, or more. Accordingly, whenplastic resin pellets are purchased in bulk, a central vacuum-poweredconveying system, powered by one or more large, high capacity industrialvacuum pumps, is a necessity.

Typically, large central plastic resin pellet conveying systems have oneor more vacuum pumps, each typically from 5 to 20 horsepower. Thesecentral systems include central controls connected by wire to eachreceiver associated with each process machine in the facility. Typicallyeight, sixteen, thirty-two or sixty-four receivers, each associated witha process machine, may be connected to and served by the central plasticresin pellet vacuum conveying system. Of course, the higher the numberof receivers served by the system, the higher the cost.

A factor to be considered in designing such a system is the speed of theplastic resin pellets as they flow through a conduit as the plasticresin pellets are carried by the moving air stream drawn by the vacuumpump. If air flow is too slow, the plastic resin pellets fall out of theair stream and lie on the bottom of the conduit, with resulting risk ofclogging the conduit. If air flow is too fast, the plastic resin pelletscan skid along the conduit surface. In such case, harder, more brittleplastic resin pellets may be damaged, resulting in dust within theconduit, which when drawn into the vacuum pump can damage the vacuumpump and render the system inoperative. Softer plastic resin pelletsheat up and can melt from friction when contacting the conduit interiorsurface. This results in “angel hair”—long, wispy-thin strands ofplastic film which eventually clog the conduit and cause the system toshut down.

For these reasons, pneumatic plastic resin pellet conveying systems mustbe designed to produce desired, reasonable conveying speeds for theplastic resin pellets.

Currently, conveying speed of the plastic resin pellets is most oftencontrolled by controlling air flow, measured in cubic feet per minute,and varying the desired and designed cubic feet per minute based onconduit diameter, with a larger diameter conduit requiring more cubicfeet per minute of air flow to maintain proper air flow speed throughthe conduit. Controlling air flow, measured in cubic feet per minute, isconventionally done by properly specifying the vacuum pump by capacityand, in some cases, by varying speed of the vacuum pump as the vacuumpump draws the air in a “vacuum” condition through the conduit, carryingplastic resin pellets in the moving, below atmospheric pressure air.Controlling cubic feet per minute of air flow is an indirect way ofcontrolling plastic resin pellet speed as the plastic resin pellets flowthrough a conduit of a given diameter.

Typically, a 2 inch diameter conduit requires about 60 cubic feet perminute of air flow to convey typical plastic resin pellets. A 2½ inchdiameter conduit typically requires about 100 cubic feet per minute ofair flow to convey typical plastic resin pellets. To achieve thesedesired air flow volume flow rates, a conventional designer mustcarefully match the horsepower of a vacuum pump, which has a given cubicfeet of air per minute rating, to a selected size conduit, taking intoconsideration the average distance the plastic resin pellets must beconveyed through the conduit from a storage silo to a receiver orloader. If this results in selection of a 5 horsepower blower/vacuumpump, then a given facility may require several such blowers/vacuumpumps, with each blower/vacuum pump supplying only a selected number ofreceivers.

A single plastic resin molding or extruding facility might theoreticallyrequire a 20 horsepower blower and the corresponding cubic feet perminute capability for the conveyance provided by the single blower tomeet the total conveying requirements for plastic resin pelletsthroughout the facility. However, a single twenty horsepower blowerwould result in far too high a conveying speed for the plastic resinpellets through any reasonable size conduit. As a result, the conveyingsystem for the plastic resin pellets in a large facility is necessarilydivided and powered by three or four smaller blowers, resulting in threeor four different, separate systems for conveyance of plastic resinpellets. Sometimes several blowers are connected to a single set ofreceivers, with one or more of the extra blowers turning “on” only whenrequired to furnish the required extra cubic feet per minute of airflow. This is controlled by a central station monitoring all receiversand all blowers, with the central station being programmed to maintainall of the hoppers associated with the process machines in a fullcondition, wherever those hoppers are located throughout the facility.

Even with careful planning and design, results achieved by suchpneumatic plastic resin pellet conveying systems are not consistent. Airflow speed and cubic feet per minute capacity of blowers often vary andare outside of selected design and specification values.

SUMMARY OF THE INVENTION

The instant invention provides an improvement to known pneumatic plasticresin pellet conveying systems, reducing the costs of those systemswhile providing consistent control of delivered cubic feet per minute ofair for individual receivers. The invention also facilitates easyexpansion of the pneumatic plastic resin pellet conveying system as thesystem grows. Such expandable systems are made feasible by an inventiveadjustable air flow limiter embodying aspects of this invention.

In one aspect of this invention, air flow control devices, mostdesirably of the type newly disclosed herein and only slightly lessdesirably of the type disclosed in co-pending U.S. patent applicationSer. No. 14/185,016 entitled “Air Flow Regulator”, filed 20 Feb. 2014 inthe name of Stephen B. Maguire, and in co-pending U.S. patentapplication Ser. No. 14/593,010 entitled “Air Flow Limiter withClosed/Open Sensing”, filed 9 Jan. 2015 in the name of Stephen B.Maguire, are added to each receiver so that the air pulled from anysingle receiver at the correct predetermined, preselected flow rate.This prevents excessive flow rates and “open” lines that dump too muchair into the system.

Use of these air flow limiters allow one large pump to be used withoutrisk to the system or to the resin being conveyed. An added advantage ofa very large pump is that it can fill multiple receivers simultaneouslywith resin. As used herein, the term “receiver” denotes the type ofapparatus disclosed in U.S. Pat. Nos. 6,089,794; 7,066,689, and8,753,432. The disclosures of these patents are hereby incorporated byreference.

The invention allows receivers to “load” the resin the instant there isdemand for material by dropping the material downwardly into agravimetric blender or directly into a process machine. The receiverneed not wait in the “queue” to load because no sequencing of thereceivers is required. Each receiver is always “ready to go.”

A central control station is not required, and neither is wiring fromeach receiver to a central control station, thus further reducing costs.As a result, there are one or several large vacuum pumps, with receiversthat stand alone without need for a central control, and an air flowlimiter on each receiver to assure proper and constant flow rate. Thisfacilitates reducing the speed of the vacuum pump, to hold the desiredvacuum level in the lines. This is in contrast to running the vacuumpump at full speed all the time.

“CFM” is a term referring to a cubic foot of air regardless of thedensity of the air. “SCFM” refers to a cubic foot of air at standardtemperature and pressure, namely 70° F. at sea level. The air flowlimiter holds SCFM constant. This means that air flow through the airflow limiter will be faster when the air is thin, such as at highaltitudes, and slower when the air is thick, such as at sea-level.However, in both cases (or any case), the air flow limiter maintainsSCFM, namely air flow in standard cubic feet per minute, constant.Stated differently, so long as the SCFM is held steady, as is the casewith an air flow limiter, the same weight of air, or number of airmolecules, flows through the limiter regardless of conditions. Air flowrate through the limiter may change in terms of the speed of the air,but in all cases the quantity of air flowing, measured in standard cubicfeet per minute, is constant.

“VFD” (Variable Frequency Drive) motors allow vacuum pumps to operate atdifferent speeds, and therefore at different CFM rates, with the vacuumpump pulling different vacuum levels depending on preset informationabout each receiver being served, and/or making adjustments based onreal time feedback of vacuum sensors located at various places in thesystem.

The addition of a SCFM (Standard Cubic Feet per Minute) air flow limiterin the air flow line allows oversized vacuum pumps to be used withoutrisk of conveying at excessive velocity. SCFM limiters restrict air flowto a preset SCFM. This maintains the desired SCFM air flow at the inlet,which is critical for proper conveying for a given size conveying line.This concept is the subject of pending U.S. patent application Ser. No.14/185,016, referenced above.

Reading vacuum levels at various points tells the controlling processorif the line is open, which means only air (and no resin material) ispresent and air is flowing unrestrictedly. This signals a loss ofmaterial at the source. A high vacuum reading indicates a plugged ornearly plugged line. Normal conditions are present where material isflowing correctly at detected mid-vacuum levels.

One line size for all receivers assures the resin transport velocity ismore likely to be in the acceptable range. However, most processesrequire the basic resin material be delivered at 50 times the rate ofadditives, such as color concentrate. Virgin (or natural) resin pelletsmay have to be loaded at a rate of 1000 pounds per hour, requiring a 2.5or 3 inch line size, while color is only required to be delivered at arate of 20 to 40 pounds an hour. A smaller receiver is used for color,namely a receiver that loads perhaps 5 pounds at a time, while thereceiver for the virgin resin material will be larger, perhaps loading50 pounds of each load cycle. A 2.5 inch line on a 5 pound receiverwould be too large. 1.5 inch line would be standard, and the use of 1.5inch resin conveying line would be better, but this risks velocitiesthat are excessive, resulting in trade-offs in design.

By placing a flow limiter at the pump suction intake, one can limit themaximum SCFM air flow to the design limit of the air flow limiterdevice; as noted this is disclosed and claimed in pending U.S. patentapplication Ser. No. 14/185,016, referenced above.

In another embodiment, one air flow limiter is in place as a single airflow limiter at the vacuum pump suction inlet with the vacuum pump beingconnected to a plurality of receivers all connected in a system. Thisprovides a selected, correct rate of air flow in standard cubic feet perminute. In this embodiment, only a single air flow limiter is used atthe vacuum pump inlet, as opposed to the alternative embodimentdescribed above where one air flow limiter is used at each receiver.

An advantage of using only a single air flow limiter of the typedisclosed herein is that the vacuum pump can be sized and operated forthe longest distance over which resin is to be conveyed in a givenlocale. This can be done while still protecting shorter runs of thesystem from excessive resin material velocity, where less vacuum isrequired. One air flow limiter costs less than having an air flowlimiter located at every receiver; this provides an advantageous aspectto this approach.

By adding an improved air flow limiter manifesting aspects of thisinvention to every receiver, plant operators can control air flow incubic feet per minute to a maintained, constant value that is ideal forthat particular receiver, considering conduit diameter and distance overwhich the plastic resin pellets must be conveyed through that conduit.Alternatively, by adding an improved air flow limiter manifestingaspects of this invention just to the suction inlet of the vacuum pump,a plant operator can control air flow in cubic feet per minute to aconstant value that is ideal for the system as a whole, consideringconduit diameter and distance over which the plastic resin pellets mustbe conveyed to the multiple receivers in the system.

Use of the improved air flow limiter in accordance with this inventionallows pneumatic plastic resin pellet conveying systems to utilize asingle large high horsepower vacuum pump. In accordance with oneembodiment of the invention, each receiver in a facility is preferablyfitted with an improved air flow limiter so the flow for each receiverin cubic feet per minute is self-limiting. This approach eliminates theneed to match vacuum pumps or blowers to a specific material conduitsize or conveyance distance. Using this approach, the improved flowlimiter permits operators to run a very large vacuum pump or blower at aspeed that will maintain a desired high level of vacuum throughout theentire vacuum (or pneumatic) plastic resin pellet conveying system.

Using larger than standard diameter vacuum conduits allows a significantvacuum reserve to exist in the plastic resin pellet conveying system,without the need for a vacuum reserve tank. Larger diameter conduitsalso mean there is little loss of vacuum over long distances, even atthe most distant receiver to which plastic resin pellets are supplied bythe system. A variable frequency drive control may be used to adjust thespeed of the vacuum pump to maintain air flow at the desired standardcubic feet per minute rate through the air flow limiter.

With the air flow limiter aspect of the invention facilitating use ofhigh horsepower vacuum pumps or blowers, designers utilizing theinvention can now design to load multiple receivers at the same timewithout fear of dropping vacuum levels too low in parts of the pneumaticor vacuum plastic resin pellet conveying system.

In the plastic resin pellet conveying system aspect of the invention, nocentral control system is required. Using the improved flow limiter,each receiver preferably controls its own operation and is not wired toany central control facility. When the level of plastic resin pellets inthe hopper of a process machine falls sufficiently low, a level sensorpreferably tells the receiver to load the hopper of the process machine.Coupled to the level sensor may be a vacuum sensor, which preferablyconfirms that the main system has sufficient vacuum available to loadthe receiver. If too many other receivers are currently loading, and thevacuum level is sensed to be below the threshold for effective loading,then the receiver associated with the sensor will wait until vacuumreadings rise. When available system vacuum is sufficient to assureadequate flow of plastic resin pellets into a given receiver, the vacuumsensor causes a vacuum valve preferably associated with the receiver toopen the connection of the receiver to the conduit carrying the plasticresin pellets, and the receiver fills with resin pellets.

In accordance with one aspect of the invention, each receiver acts onits own sensed information. Use of the high horsepower vacuum pump meansthat several receivers can load simultaneously.

The improved air flow limiter does several things to make such systemspossible. By limiting cubic feet per minute of flow to a desiredconstant level, there is virtually no limit on the horsepower of thevacuum pump. The risk of a too high a conveyance speed of the plasticresin pellets through the conduit is eliminated. Additionally, if areceiver is not drawing in plastic resin pellets but is just drawing airas a result of the main supply of plastic resin pellets being exhausted,the empty conduit of the conveying system would ordinarily convey asubstantial amount of air, which normally would drop the vacuum reserveof the entire pneumatic conveying system very rapidly. But with the airflow limiter, such dumping of air into the conveying conduit is at leastsubstantially reduced, and if the air flow limiter is at the suctionintake of the vacuum pump, such dumping of air into the system isessentially impossible.

Further contributing to minimized air dump into the vacuum conduit isthe ability of the receiver to detect system failure or absence ofmaterial being loaded, thereby stopping further load cycles and soundingan alarm.

In the air flow limiter aspect of the invention, the limiter preferablyhas a valve which relies on two opposing forces, gravity in onedirection and “lift” created by air flow in the opposite direction.Because the improved air flow limiter uses gravity to close the valveportion of the limiter, orientation of the air flow limiter isimportant. Air flow must be upward, essentially vertically through theair flow limiter, to counter the downward force of gravity.

The improved air flow limiter is desirably in the form of a tube with anair flow actuated valve within the tube. In a “no flow” condition,gravity holds the valve closed. However, as air flow through the limiterreaches a pre-selected design value, air flowing over and against asail-like plate lifts an internal free floating valve. This shuts offair flow through the air flow limiter if the free floating valve risessufficiently to contact an adjustable stop located within the tube. Inone position, the adjustable stop provides for some air flow through theair flow limiter when the free floating valve has contacted the stop. Ina second position of the adjustable stop, once the free floating valvecontacts the stop in the second position, no air flow can flow throughthe air flow limiter.

By adjusting the size and/or shape of the “sail”, and/or the weight ofthe free floating valve, and/or the position of the adjustable stop,desired air flow in standard feet per minute can be regulated veryclosely. Gravity as a force in one direction means the opening force isconstant over the full range of motion of the valve device. (A spring,if one were used, would provide a variable force. However, use ofgravity in the air flow limiter aspect of the invention eliminates thatvariable).

In the air flow limiter aspect of the invention, at the desired designstandard cubic feet per minute of air flow, the valve opens as air liftsit. The valve would continue moving upwardly except for the fact thatthe valve reaches a point of air flow restriction, where the valve holdsair flow steady at the desired design value. If the valve moves furtherupwardly in response to additional air flow, to either a first positionat which the adjustable stop contacts the valve and the valve remainspartially open, or if the valve moves further upwardly and contacts thestop when the stop is at a second position which is preferably a “valveclosed” position, this either reduces air flow and resulting force inthe valve (if the valve contacts the stop at the first position) orstops all air flow through the limiter (if the stop is at the secondposition). The valve may then drop in response to gravity.

If the valve drops below the position corresponding to the designed airflow level, this allows more air flow and consequently the valve risesas the air pushes the valve upwardly. As a result, the valve reaches thedesired design valve equilibrium control point essentially instantly andvery accurately. A detector of the type disclosed in the aforementioned'010 application may be used to detect position of the valve and may beused to actuate the stop to change the stop from the first stop positionto the second position, if desired.

Known air flow shutoffs are subject to “vacuum pull”, causing them toshut off completely once air begins to flow. This is because in knownshutoffs, vacuum “pull” of the vacuum pump is always present. In the airflow limiter of the invention, a short vertical tube closes against aflat horizontal surface. In the air flow limiter of the invention, airflow is directed through the center of the short tube and escapes overthe top edge of the short tube and then around open edges of a flatshutoff surface. A flat, desirably triangular or star-shaped plate ispositioned in the air flow below and connected to the short tube. Thisplate acts as a sail in the air flow and will, at the designed desiredstandard cubic feet per minute air flow rate, provide enough lift toraise the short tube against either the stop if the stop is at the firstposition or the stop and the shutoff plate if the stop is at the secondposition where the stop is at least flush with and perhaps withdrawnslightly from the plane of the shutoff plate.

At complete shut off, with the stop at the second position and therebybeing at least flush and perhaps withdrawn from the flat shutoff platesurface, with vacuum above the flat plate shutoff surface and air atsome pressure below the flat shutoff plate surface, most of the airpressure forces are against the walls of the short tube. Those forcesare radially outwardly directed. Specifically, they are horizontal dueto the configuration of the air flow limiter, and do not exert verticalforce that would make the movable portion of the valve, namely the shorttube, move in a vertical direction.

The surface of the end of the short tube, at the short tube end edge, isa horizontal surface and can provide a small vertical force on the tubewhen air travelling upwards impinges on the surface. For this reason,the air flow limiter of the invention uses a very thin wall short tube,to minimize this horizontal surface area of the short tube.

In the air flow limiter of the invention, air flow rate in cubic feetper minute can be adjusted by adding or subtracting weight from thefloating valve, or by adjusting the surface area of the sail, or byadjusting the size or shape of the sail in the air flow or by adjustingthe position of the “stop” against which the floating valve abuts at anextremity position of valve travel.

Accordingly, in one of its aspects, the invention provides a resindelivery system and method that includes an air flow limiter having apreferably vertically oriented tube, a pair of open-ended preferablytelescoping tubular internal segments within the tube, with an outertubular segment preferably being fixed and the other preferably beingslidably moveable along the fixed segment in the axial direction. Theair flow limiter further includes a plate extending partially across theinterior of the vertically oriented tube and positioned for contactingthe moveable one of the telescoping tubular segments and limiting travelof the moveable telescoping tubular segment, with the plate covering theupper, open end of the moveable telescoping tubular segment upon contacttherewith.

In this aspect, the invention preferably yet further includes a sailpositioned in the vertically oriented tube below the telescopingsegments and a strut preferably connecting the sail and the moveabletelescoping tubular segment. A baffle may be provided and preferably bepositioned to direct upward air flow within the tube through thetelescoping tubular segments. The moveable telescoping tubular segmentpreferably moves vertically within the tube, unitarily with the sail,responsively to air flow upwardly through the tube against the sail.

The air flow limiter of the invention in one of its aspects furtherprovides an actuator connected to the plate for selectively limitingtravel of the moveable tubular segment with the actuator providing a“stop” in at least two positions. In one extended position, theactuator, which is preferably a solenoid, extends the stop to limittravel of the moving telescopic tubular segment to a degree that airflow is still permitted through the limiter; at a second position, thestop is desirably flush with or withdrawn into the plate defining theextreme upper limit of travel of the stop. The stop is preferablyprovided in the form of a piston portion of a solenoid, with thesolenoid actuating the piston between the first and second positionsdefining the stop.

The tubular segments are preferably cylindrical; the surface of theplate contacted by the moveable tubular segment is preferably planar;and the portion of the moveable tubular segment contacting the platesurface is preferably annular. A detector portion of the limiter, ifprovided, preferably detects an electromagnetic beam, most preferably avisible light beam or an infrared beam to determine when the portion ofthe moveable tubular segment has contacted the plate surface.

In a variation of terminology, a surface of the plate contacted by themoveable tubular segment is flat, the tubular segments are cylindricaland the circular edge of the tubular segment contacting the plateservice is annular and normal to the axis of the tubular segment.

In yet another one of its aspects, this invention provides a resindelivery system having at least one adjustable air flow limiterconsisting of a vertically oriented tube, a tubular segment within thetube, which segment is moveable in the axial direction, a plateextending at least partially across the interior of the tube forcontacting the movable tubular segment and defining a limit of travel ofthe moveable tubular segment, a sail positioned in the tube below themoveable tubular segment and being moveable vertically within the tube,and a strut connecting the tubular segment and the sail, with a stop forlimiting travel of the moveable tubular segment being adjustably mountedon the plate for providing two limits of travel for the moveable tubularsegment. A baffle may be provided connected to and located within thetube defining a lower limit of travel of the moveable tubular segmentupon contact of the strut with an upper extremity of the baffle. Themoveable tubular segment is in sliding telescoping engagement with thetubular portion of the baffle, directing upward air flow within thetube, with the moveable tubular segment being moveable unitarily withthe sail in response to upward air flow through the tube contacting thesail.

In yet another one of its aspects, this invention provides a resindelivery system that includes at least one air flow limiter, which ispreferably adjustable, having a vertically oriented tube with a sailassembly positioned in the tube and moveable therewithin responsively toair flow through the tube to regulate air flow through the tube and tostop air flow thorough the tube upon air flow exceeding a preselectedvalue expressed in standard cubic feet per minute.

In yet another one of its aspects, this invention provides a method forconveying granular plastic resin by controlled air flow where air flowcontrol involves the steps of providing a vertically oriented tube,positioning a moveable sail assembly including a sail within the tube,positioning an adjustable stop within the tube, and permitting the sailassembly to move responsively to air flow through the tube between aposition at which air flows around the sail assembly and through thetube, and a position at which the sail assembly contacts the stop andblocks air flow through the tube.

In yet another one of its aspects, this invention provides a pneumaticresin delivery system utilizing air flow limiting apparatus including avertically oriented first tube, a vertically oriented second tube whichis moveable along and within the first tube, a guide within the firsttube for limiting the second tube to vertical co-axial movement withinand relative to the first tube, a sail within the first tube beingconnected to the second tube and being moveable responsively to air flowwithin the first tube, and a moveable, adjustable stop within andconnected to the first tube for limiting vertically upward travel of thesecond tube.

In still another one of its aspects, this invention provides apparatusfor conveying granular plastic resin from a supply to receivers thatretain and dispense the resin when needed by a process machine, wherethe apparatus includes a vacuum pump, an adjustable single air flowlimiter connected to a suction head of the vacuum pump, a first conduitconnecting the receivers to the air flow limiter, and a second conduitconnecting the granular material supply to the receivers. In thisembodiment of apparatus of the invention, suction created by operationof the vacuum pump draws granular plastic resin from the supply into thereceivers through the second conduit and draws air from the secondconduit through the receivers, the first conduit and the air flowlimiter. The air flow limiter is oriented in a vertical direction forvertical flow of air upwardly therethrough. An emitter-detectorcombination may be provided and, if so, is preferably oriented toprovide a beam within and passing through a tubular housing portion ofthe air flow limiter with the beam preferably being perpendicular to theair flow limiter axis. The adjustable feature of the single air flowlimiter is preferably provided by a solenoid mounted so that thesolenoid piston moves between first and second positions thereby toadjust the limit of travel for a moveable valve member portion of theair flow limiter.

In yet still another aspect, this invention provides apparatus forconveying granular plastic resin material from a supply of resinmaterial to receivers that retain and dispense the resin material whenneeded by a process machine, where the apparatus includes a vacuum pump,air flow limiters connected to outlets of the receivers, with the airflow limiters being vertically oriented for vertical flow of air drawnby suction therethrough, a first conduit connecting the air flowlimiters to a suction head of the vacuum pump and a second conduitconnecting the granular resin material supply to the receivers. In thisapparatus aspect of the invention, suction created by operation of thevacuum pump draws granular plastic resin from the supply of granularplastic resin material into the receivers through the second conduit,and also draws air from the second conduit through the receivers, theair limiters, and the first conduit. In this second embodiment, at leastone of the air flow limiters preferably consists of a tube, a tubularsegment within the tube that is moveable in the axial verticaldirection, a plate extending at least partially across the interior ofthe tube for contacting the moveable tubular segment in combination witha solenoid mounted on the plate, with the solenoid piston defining alimit of vertical travel of the moveable tubular segment when thesolenoid piston is extended and the plate and solenoid together defininga limit of vertical travel of the moveable tubular segment when thesolenoid piston is retracted, a sail connected to the moveable tubularsegment and being moveable therewith within the tube, and a baffleconnected to and within the tube defining a second limit of verticaltravel of the moveable tubular segment, where the moveable tubularsegment is in sliding telescoping engagement with a tubular portion ofthe baffle. The moveable tubular segment moves unitarily with the sailin response to vertical air flow through the tube contacting the sail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a resin delivery system with asingle air flow regulator in accordance with aspects of the invention.

FIG. 2 is a schematic representation of a resin delivery system with aplurality of air flow regulators in accordance with aspects of thisinvention.

FIG. 3 is an isometric view of the exterior of an air flow limiterportion of apparatus for pneumatically conveying granular plastic resinas disclosed in co-pending application Ser. Nos. 14/185,016 and14/574,561 referenced above.

FIG. 4 is a front elevation of the air flow limiter illustrated in FIG.3.

FIG. 5 is an isometric sectional view of the air flow limiterillustrated in FIGS. 3 and 4, with the section taken at arrows 3-3 inFIG. 4.

FIG. 6 is a sectional view in elevation of the air flow limiterillustrated in FIGS. 3 and 5, with the section taken at lines and arrows3-3 in FIG. 4, with air flow through the air flow limiter being depictedin FIG. 6 by curved dark arrows.

FIG. 7 is a sectional view in elevation, similar to FIG. 6, of the airflow limiter illustrated in FIGS. 3 through 6, but with the air flowlimiter internal parts in position whereby there is no air entering theair flow limiter and hence there is no air flow upwardly through the airflow limiter, in contrast to the condition with such air flow shown inFIG. 6.

FIG. 8 is a sectional view in elevation, similar to FIGS. 6 and 7 of theair flow limiter illustrated in FIGS. 3 through 7, but with the air flowlimiter internal parts in position where there is an excessive amount ofair attempting to enter the air flow limited but there is no air flowupwardly through the air flow limiter due to the air flow limiter valvehaving moved to block air flow upwardly through the air flow limiter, incontrast to air flow upwardly through the air flow limiter as shown inFIG. 4.

FIG. 9 is an exploded isometric view of the air flow limiter illustratedin FIGS. 3 through 8.

FIG. 10 is an isometric view of the movable portion of the air flowlimiter illustrated in FIGS. 3 through 9.

FIG. 11 is a sectional view of an air flow limiter similar to FIGS. 6, 7and 8, illustrating an alternate construction of the baffle portion ofthe air flow limiter.

FIG. 12 is sectional view of the air flow limiter similar to FIGS. 6, 7,and 11, illustrating a second alternate construction of the baffleportion of the air flow limiter.

FIG. 13 is a sectional view of an air flow limiter of the type disclosedin co-pending U.S. patent application Ser. No. 14/593,010, with thesectional view being taken in elevation, similarly to FIG. 7, with anelectromagnetic beam detecting position of the movable valve portion ofthe air flow limiter.

FIG. 14 is a sectional view in elevation, similar to FIG. 13, of the airflow limiter disclosed in FIG. 13 and in co-pending U.S. patentapplication Ser. No. 14/593,010, with the detector beam being blocked bythe moveable valve portion of the air flow limiter, thereby indicatingno air flow through the air flow limiter.

FIG. 15 is a sectional view in elevation, similar to FIG. 7, of anadjustable air flow limiter in accordance with the invention, with theair flow limiter internal parts in position whereby a moderate amount ofair is entering the air flow limiter, the sail assembly has been liftedby air flow, and the air flow limiter internal valve has not contacted a“stop” defining an intermediate valve position and hence an intermediatemaximum air flow rate through the air flow limiter.

FIG. 16 is a sectional view in elevation of the adjustable air flowlimiter illustrated in FIG. 15, with the “stop” illustrated in FIG. 15withdrawn and the air flow limiter internal parts in position whereby noair can flow through the air flow limiter due to those internal partsnow having blocked air flow due to instantaneous air flow exceeding themaximum design value.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE KNOWN FOR PRACTICEOF THE INVENTION

In this application, unless otherwise apparent from the context it is tobe understood that the use of the term “vacuum” means “air at slightlybelow atmospheric pressure.” The “vacuum” (meaning air at slightly belowatmospheric pressure) provides a suction effect that is used to drawgranular plastic resin material out of a supply and to convey thatgranular plastic resin material through various conduits to receiverswhere the granular resin material can be temporarily stored before beingmolded or extruded. Hence, when reading this application it is usefulfor the reader mentally to equate the term “vacuum” with the term“suction”.

This invention provides an improvement on the air flow limitersdisclosed and claimed in pending U.S. patent application Ser. Nos.14/185,016 and 14/593,010 referenced above.

With the improved air flow limiter of this invention, there areeffectively two “design limits” where “design limit” denotes the maximumair flow allowable through the air flow limiter. In the air flow limiterof the invention, a first “design limit” occurs an air flow through theair flow limiter is sufficient to move moveable sail 34 and hencemoveable internal segment 42 upwardly to a position at which moveableinternal tubular segment and the assembly of first and second struts 48,50 contact piston 124 of solenoid 120, when piston 124 is extended fromsolenoid 120 and is at the position illustrated in FIG. 15. When theassembly of first and second struts 48, 50 moves slightly upwardly fromthe position illustrated in FIG. 15 and contacts the lower extremity ofpiston 124, when piston 124 is extended from solenoid 120 as illustratedin FIG. 14, this defines a first “design limit.” Air flow through airflow limiter 30″ when the assembly of struts 48, 50 contacts the lowerextremity of piston 124 when extended is one of the two “design limits.”The second design limit occurs when the assembly of struts 48, 50 isjust below and about to touch flow limiting plate 46. With air flowthrough flow limiter 56 with the struts 48, 50 at that position, airflow though limiter 30″ is at a maximum. Once air flow increases evenslightly, the air flow impinging sail 34 pushes assembly of struts 48,50 and hence moveable tubular segment 42 upwardly against flow limitingplate 46, and flow through flow limiter stops. Consequently, the airflow through limiter 30″ when the upper extremity of moveable tubularsegment 42 is just short of flow limiting plate defines the second“design limit” of air flow through limiter 30″.

Regarding nomenclature, “30” denotes the limiter illustrated in FIGS. 1through 12; “30′” denotes the limiter illustrated in FIGS. 13 and 14;and “30” denotes the limiter illustrated in FIGS. 15 and 16. With thelarge number of common parts and operating characteristics common tothese three limiters, sometimes the designators “30” and “30 etc.” areused to refer to all of these limiters; the context makes clear as towhen a specific characteristic of one of the limiter is the subject ofthe text.

When air flow is below the first design limit, limiter 30 remains fullyopen. The moment air flow equals the first design limit, the assembly ofstruts 48, 50 carrying moveable tubular segment 42 contacts the circularsurface, unnumbered in the drawings, of piston 124 when piston 124 is inits extended position relative to solenoid 120. So long as piston 124remains extended from solenoid 120, air flow through limiters 30 etc.cannot exceed the first design limit. However, once solenoid 120 isde-actuated and piston 124 retracts into solenoid 120 to the positionillustrated in FIG. 16, air flow through limiters 30 etc. can increaseup to the second design limit which, as noted above, occurs as moveableinternal tubular segment 42 is approaching and in close proximity toflow limiting horizontal plate 46.

Apparatus for conveying granular plastic resin material from the supplyto receivers that retain and dispense the resin material when needed bya process machine is illustrated in FIG. 1. The apparatus, which isdesignated generally 88 in FIG. 1, preferably includes a vacuum pumpdesignated generally 92 and shown schematically in FIG. 1. The vacuumpump preferably includes a vacuum pump suction head 93 also shownschematically in FIG. 1. Connected to the vacuum pump suction head 93 isan airflow limiter 30 shown only in schematic form in FIG. 1, but shownin detail in various forms in FIGS. 3 through 16. Airflow limiter 30receives vacuum drawn by vacuum pump 92 through vacuum drawing conduit100.

Vacuum drawing conduit 100 is connected to a plurality of receivers 16,each of which receives, retains and dispenses, as needed, granularplastic resin material to a process machine, such as a granulatorblender, or an extruder, or a molding press preferably located below areceiver 16. The process machines are not illustrated in FIG. 1 toenhance the clarity of the drawing.

Further illustrated in FIG. 1 is a hopper 18 for storage of granularplastic resin material therein and a resin conveying conduit 98, whichserves to draw resin from hopper 18 and to deliver the resin throughresin conveying conduit 98 to the respective receivers as vacuum isdrawn by the vacuum pump, with vacuum propagating through air flowlimiter 30, vacuum drawing conduit 100, the various receivers 16, andresin conveying conduit 98, back to hopper 18.

FIG. 2 shows an alternate embodiment of a resin conveying systemdesignated 88A. FIG. 2, like FIG. 1, depicts a vacuum pump 92 shown inschematic form having a vacuum pump suction head 93 also depicted inschematic form. In the alternate embodiment illustrated in FIG. 2,vacuum drawing conduit 100 leads directly into and communicates withvacuum pump suction head 93. In the embodiment illustrated in FIG. 2, anair flow limiter 30 is provided for each receiver 16, with the air flowlimiter 30 for a respective receiver 16 being located in a portion of aconnection conduit 102 that connects a respective receiver to vacuumdrawing conduit 100. In FIG. 2, each air flow limiter 30 is depicted ina vertical orientation, just as is airflow limiter 30 depicted in avertical orientation in FIG. 1. Each receiver is connected by connectionconduit 102 to vacuum drawing conduit 100 with air flow limiter 30forming a portion of connection conduit 102.

In FIG. 2, as in FIG. 1, a first conduit 98 serves to convey granularplastic resin from hopper 18 to the respective receivers in response tovacuum drawn by vacuum pump 92 as that vacuum propagates from vacuumpump 92 through second conduit 100, connection conduits 102, receivers16, and resin conveying conduit 98 to hopper 18.

During operation of the resin conveying systems shown schematically inFIGS. 1 and 2, upon actuation of vacuum pump 92, a vacuum is drawn atvacuum pump suction head 93. This vacuum, as it propagates back tohopper 18, serves to draw resin out of hopper 18 and into the respectivereceivers 16. In the embodiment illustrated in FIG. 2, individual airflow limiters 30 limit the suction or vacuum drawn by vacuum pump 92through a given associated receiver 16. In the embodiment illustrated inFIG. 1, a single air flow limiter 30 limits the vacuum drawn through allof receivers 16 of the granular resin conveying system illustrated inFIG. 1.

Referring to FIGS. 1 and 2, the air flow limiter 30 portion of the resindelivery systems is preferably in the general form of a verticallyoriented tube, preferably having inlet and outlet ends 54, 56respectively. The tubular character of air flow limiter 30 is apparentfrom FIGS. 3 through 16, where air flow limiter 30 preferably includes avertically oriented exterior tube 32, with open-end caps 58, 60 definingand providing open inlet and outlet ends 54, 56 respectively. End caps58, 60 are open, of generally cylindrical configuration, and areconfigured to fit closely about vertically oriented tube 32 so as toprovide a substantially air tight fit between end caps 54, 56 and tube32.

As illustrated in FIG. 5, air flow limiter 30 preferably includes,within vertically oriented exterior tube 32, a horizontally positionedplate 46, which is oriented perpendicularly to the axis of tube 32.Plate 46 is preferably configured as a circular disk of lesser diameterthan the inner diameter of vertically oriented tube 32, with plate 46further preferably including three legs extending outwardly from thecircular interior disk portion of plate 46. Legs of plate 46 aredesignated 62 in FIG. 9, while the circular interior portion of plate 46is designated 64 in FIG. 9. Plate 46 is secured to the interior ofvertically oriented outer tube 32 by attachment of legs 62 to theinterior surface of tube 32. Any suitable means of attachment, such asby welding, adhesive, mechanical screws, or end portion of legs 62defining tabs fitting into slots within tube 32 as shown in FIG. 5, maybe used.

As shown in FIGS. 5, 6, and 7, a baffle 52 is positioned withinvertically oriented outer tube 32, below plate 46. Baffle 52 has a lowerconical portion 66 and an upper cylindrical portion 44, with cylindricalportion 44 defining a fixed internal tubular segment of air flow limiter30. Baffle 52 is preferably retained in position by a pair of screwsdesignated 68, 70 respectively. Baffle 52 preferably rests on screw 68.Screw 70 preferably fits against the fixed internal tubular segment 44portion of baffle 52 to secure baffle 52 in position within verticallyoriented external tube 32. Lateral force applied by screw 70 in adirection perpendicular to the axis of vertically oriented external tube32, with screw 70 in contact with fixed internal tubular segment 44,serves to effectively retain baffle 52 against movement withinvertically oriented external tube 32.

The upper portion of baffle 52, defining fixed internal tubular segment44, is adapted for sliding telescopic engagement with and movementtherealong by movable tubular segment 42. Fixed to movable tubularsegment 42 is a first strut 48 preferably extending transversally acrossthe upper portion of movable tubular segment 42 and preferably securedon either end to movable tubular segment 42, as illustrated in FIG. 10.Preferably extending downwardly from first strut 48 is a second strut50, preferably secured to first strut 48 and preferably also to a sail34, as illustrated in FIG. 10 and in FIGS. 5, 6, 7, 8 and 9.

Movable sail 34 is preferably planar and positioned fixedly on secondstrut 50 to remain perpendicular with respect to the axis of verticallyoriented outer tube 32. Movable sail 34 is preferably of generallytriangular configuration, as illustrated in FIGS. 9 and 10, with thesides of the triangle curving slightly inwardly. The curved edges 72 ofmovable sail 34 converge and terminate to form small rectangular shapedextremities of sail 34, which are designated 76 in FIG. 9.

Movable sail 34 is positioned within generally vertically oriented outertube 32 so that rectangular extremities 76 are closely adjacent to butdo not contact the inner surface of vertically oriented outer tube 32,so long as sail 34 moves vertically up and down within verticallyoriented external tube 32. The rectangular shape of extremities 76 withtheir outwardly facing planar surface assures minimal friction andconsequent minimal resistance to movement of movable sail 34 in theevent one of rectangular extremities 76 contacts the interior surface ofvertically oriented tube 32, should sail 34 for some reason movelaterally or otherwise and become skew to the vertical axis of tube 32.

Movable internal tubular segment 42 is telescopically movable, unitarilywith sail 34, relative to and along fixed internal tubular segment 44. Alower limit of movement of movable tubular segment 42 is illustrated inFIG. 7, where the first strut portion 48 of movable tubular segment 42(shown in FIG. 10) rests on the upper circular edge of fixed internaltubular segment 44. This is the condition when no air is flowing ordrawn through the air flow limiter and gravity causes sail 34 togetherwith movable internal tubular segment 42 to drop, with first strut 48coming to rest on the upper circular edge of fixed tubular segment 44.

When air is flowing through air flow limiter 30, as illustratedgenerally in FIG. 6, the moving air pushes against movable sail 34,moving it upwardly. Movable internal tubular segment 42 moves upwardlyunitarily with sail 34 due to the fixed connection of movable tubularsegment 42 and movable sail 34 made via first and second struts 48, 50,as illustrated in FIGS. 5, 6, 7, 9, and 10.

Referring to FIGS. 15 and 16, if air flow upwardly through air flowlimiter 30″ reaches a first, preselected design limit, air flowcontacting sail 34 pushes sail 34 upwardly so that the top of firststrut 48 contacts circularly downwardly facing surface of piston 124extending from solenoid 120. In this condition, with piston 124 beingextended from solenoid 120 and held in position by action of solenoid120, the first selected design limit air flow can pass through limiter30″ by passing upwardly past sail 34 through moveable tubular segment42, around edge 82 of flow limiter plate 46 and then out of flow limiter30″. So long as piston 124 remains extended from solenoid 120, air canflow through limiter 30″ with the air flow rate being up to thepreselected first design limit.

If piston 124 is retracted into solenoid 120 such that the circulardownwardly facing surface of piston 124 is at least flush with the lowersurface of flow limiting horizontal plate 46, additional air, over andabove the air flow defining the first design limit, can flow throughlimiter 30″. Air can flow through limiter 30″ against sail 34 andthrough moveable tubular segment 42 and around flow limiting plate 46 inan amount up to the second design limit. When flow reaches the seconddesign limit, air flow is sufficient to push moveable sail 34 upwardlyso that the top of first strut 48 contacts retracted piston 124 residingwithin solenoid 120 and the upwardly extending edges of moveable tubularsegment 42 contact the lower facing surface of plate 46, therebystopping air flow through limiter 30″. In this condition, which isillustrated in FIG. 8, no air can pass between the upper annular edge 78of movable tubular segment 42 and flow limiting horizontal plate 46, andair flow stops.

Once air flow stops through vertically oriented outer tube 32, gravitypulling downwardly on sail 34, connected movable internal tubularsegment 42, and first and second struts 48, 50, causes these parts,which may be connected together and fabricated as a single integralassembly as shown in FIG. 8, to move downwardly, thereby againpermitting air flow upwardly through air flow limiter 30 etc. asdepicted generally in FIG. 6. Consequently, air flow limiter 30 etc. isself-regulating in that when air flow exceeds the second design limit,the force of air moving or impinging on sail 34 pushes movable internaltubular segment 42 upwardly until upper annular edge 78 of movabletubular segment 42 contacts plate 46 and no air can then escape upwardlybetween the upper annular edge 78 of movable tubular segment 42 andplate 46. This stops air flow through flow limiter 30 etc. untildownward movement of sail 34 unitarily with movable internal tubularsegment 42 moves upper annular edge 78 of movable tubular segment 42away from plate 46, again permitting air to flow through the upperextremity of movable tubular segment 42, with air passing between upperannular edge 78 of movable internal tubular segment 42 and flow limitinghorizontal plate 46, and then escaping through upper outlet end 56 ofair flow limiter 30″.

Air flow limiter 30″ is also self-regulating when solenoid 120 has beenactuated by energizing coil 122 and piston 124 has emerged from solenoid120 as a result. In this condition, air flow limiter 30″ is againself-regulating in that air flow cannot exceed the first design limit solong as piston 124 is extended from solenoid 120. The force of airmoving or impinging on sail 34 pushes moveable internal tubular segment42 upwardly until the top of first strut 48, which has been illustratedas the head of a machine screw, contacts extended piston 124. Hence, theassembly of sail 34, first and second struts 48, 50 and moveable tubularsegment 42 may move between the position of no air flow, illustrated inFIG. 7, and the position at which first strut 48 contacts extendingpiston 124, thereby permitting air flow up to the first design limitthrough flow limiter 30, due to the space between the upper edges of thecylindrical surface of moveable tubular segment 42 and flow limitingplate 46.

With the self-regulating characteristic of air flow limiter 30, theassembly consisting of movable internal tubular segment 42, first andsecond struts 48, 50 and sail 34 may oscillate somewhat about theposition at which air flow drawn by suction is at the desired level, asthe vacuum pump drawing air through flow limiter 30 varies in cubic feetper minute of air drawn.

Desirably, ends of first strut 48, which is depicted as beinghorizontally disposed in the drawings, are mounted in movable tubularsegment 42 in movable fashion such that first strut 48 can moveslightly, rotationally, relative to movable internal segment 42. This isto provide a small amount of “play” in the event movable sail 34 andsecond strut 50, which is vertically oriented and connected to movablesail 34, become skew with respect to the vertical axis of verticallyoriented exterior tube 32. Should this occur, the movable characteristicof first strut 48, being slightly rotatable relative to movable internaltubular segment 42, effectively precludes movable internal tubularsegment 42 from binding with respect to fixed internal tubular segment44 and thereby being restricted from what would otherwise be freelytelescoping movement of movable internal tubular segment 42 relative tofixed internal tubular segment 44.

Desirably first strut 48 is rotatable relative to movable internaltubular segment 42, to provide maximum freedom of vertical motion ofmovable internal tubular segment 42 in the event movable sail 34 becomesskew to the axis of vertically oriented exterior tube 32, withconsequent frictional force restricting vertical movement of movablesail 34.

Baffle 52 preferably includes two portions, the upper portion preferablybeing defined by fixed internal tubular segment 44 and a lower portionpreferably being defined by conical portion 66 of baffle 52. A loweredge of baffle 52 is circular and is designated 84 in the drawings.Circular edge 84 fits closely against the annular interior wall ofvertically oriented exterior tube 32 so that all air passing upwardlythrough air flow limiter 30, namely through vertically oriented exteriortube 32, is constrained to flow through the interior of baffle 52. Thetight fitting of the circular lower edge of baffle 52 against theinterior wall of vertically oriented exterior tube 32 forces all airentering flow limiter 30 from the bottom to flow through the interior ofbaffle 52, flowing upwardly through lower conical portion 66 of baffle52.

The air then flows further upwardly through the interior of fixedinternal tubular segment 44. Thereafter, if movable internal tubularsegment 42 is spaced away from flow limiting horizontal plate 46, airflows along the surface of movable internal tubular segment 42, passingthe upper annular edge 78 of movable internal tubular segment 42; airthen flows around the space between edge 82 of flow limiting horizontalplate 46 and the interior annular wall of vertically oriented exteriortube 32. The air then flows out of air flow limiter 30 via open outletend 56 formed in end cap 60.

In an alternate embodiment of air flow limiter 30 etc., baffle 52 may beconstructed from two pieces that fit closely together, with the twopieces being in facing contact in the area where they define fixedinternal tubular segment 44, but diverging one from another in the areawhere they define conical portion 66 of baffle 52. As illustrated inFIG. 12, the two portions of baffle 52 are designated “66A” and “66B”where they diverge, with baffle portion 66A serving to channel air flowupwardly through vertically oriented exterior tube 32 into fixedinternal tubular segment portion 44 of baffle 52. The space between thelower parts of baffle portions 66A and 66B is filled with a fillermaterial 86 to provide additional assurance that all air enteringvertically oriented exterior tube 32 from the bottom flows through fixedinternal tubular segment 44 and on through movable internal tubularsegment 42, and does not pass around the edge of baffle 52, namelybetween baffle 52 and the interior surface of vertically orientedexterior tube 32. Filler material 86 provides additional structuralrigidity for flow limiter 30.

In another alternative environment of air flow limiter 30 etc., baffle52 is one piece, preferably molded plastic, as illustrated in FIG. 11,where baffle 52 is designated 52B to distinguish it from the baffleconstruction illustrated in FIG. 12 and the baffle constructionillustrated in the other drawing figures. In the baffle constructionillustrated in FIG. 11, the one piece construction means that there isno need or space for any filler material.

The assembly illustrated in FIG. 10 comprising the moveable internaltubular segment 42, first strut 48, second strut 50 and moveable sail 34may preferably be constructed as a single piece or several pieces asrequired. The assembly of moveable internal segment 42, first and secondstruts, 48, 50 and moveable sail 34 is referred to as a “sail assembly.”It is not required that first and second struts 48, 50 be separatepieces; they may be fabricated as a single piece. Additionally, secondstrut 50, which has been illustrated as a machine screw in FIGS. 9 and10, need not be a machine screw. Any suitable structure can be used forsecond strut 50 and it is particularly desirable to fabricate first andsecond struts 48 and 50 from a single piece of plastic or metal, bymolding, by machining, by welding, or by otherwise fastening two piecestogether. Similarly with the hex nut, which is unnumbered in FIG. 10 andillustrated there, any other suitable means for attachment of the secondstrut or a vertical portion of a strut assembly to moveable sail 34 maybe used.

Referring to FIGS. 13 and 14, an air flow limiter in accordance withapplication Ser. No. 14/593,010, has been designated generally 30′ andincludes a vertically oriented exterior tube 32 and a moveable sail 34.These components are preferably the same as those described with respectto air flow limiter 30 above. Air flow limiter 30′ further includes apair of concentric telescoping tubular segments 40, a moveable internaltubular segment 42, a fixed internal tubular segment 44, a flow limitinghorizontal plate 46, first and second struts 48, 50, a baffle 52, and aninlet end 54 and an outlet end 56, all preferably the same as the airflow limiter illustrated in the other drawing figures and as describedabove. Other parts that are shown in FIGS. 13 and 14, and that appear tobe identical to corresponding parts shown in FIGS. 3 through 12, areidentical and are not further delineated herein for the sake of somebrevity.

Air flow limiter 30′ illustrated in FIGS. 13 and 14 includes an emitter114 and a detector 116, with emitter 114 emitting an electromagneticbeam 118 with the beam being detected by detector 116 when the beamimpinges thereon. A housing 110 is provided for emitter 114. A housing112 is provided for detector 116. Housings 110, 112, emitter 114, anddetector 116 may be secured to the tubular portion of air flow limiter30′ by any suitable means. The detector detects when the electromagneticbeam has been intersected by the moveable portion of the air flowlimiter, thereby providing an indication as to whether the air flowlimiter has reached the second design value. It is within the scope ofthe invention to position emitter 114 and detector 116 differently so asto detect the position of moveable tubular segment 42 at variouspositions.

Referring to FIGS. 15 and 16, an air flow limiter in accordance withthis invention has been designated generally 30″ and includes avertically oriented exterior tube 32 and a moveable sail 34, with thesecomponent being preferably the same as those described with respect toair flow limiters 30 and 30′ above. Similarly to air flow limiter 30′,air flow limiter 30″ includes a pair of concentric telescopic tubularsegments 40. Other parts that are shown in FIGS. 15 and 16, and thatappear to be identical to corresponding parts shown in FIGS. 3 through14, are identical and are not further delineated herein for the sake ofsome brevity.

Air flow limiter 30 etc. preferably contains no springs. Air flowlimiter 30 etc. preferably contains no sensors to provide operatingfeedback to a control device for regulation of air flow limiter 30 etc.;no feedback control sensors are needed since because air flow limiter 30etc. is self-regulating, and once in place, an air flow limiter is notsubject to outside intervention or control, other than actuation ofsolenoid 120 to extend piston 124 therefrom to adjust the operation ofair flow limiter 30″. Air flow limiter 30 etc. preferably includes atubular valve, closing against a flat surface, where the tubular valveis defined by movable internal tubular segment 42 closing against flowlimiting horizontal plate 46. Movable internal tubular segment 42 is inthe form of an open-ended cylinder and is connected to a plate in theform of movable sail 34 to move movable tubular segment 42 against flowlimiting horizontal plate 46. Air flow limiter 30 etc. uses gravityalone to open the valve defined by the assembly of movable internaltubular segment 42, movable sail 34, and the connecting structuretherebetween.

In the air flow limiter 30 etc. illustrated in FIGS. 3 through 16, themovable internal tubular segment 42 is preferably made with a very thinwall, preferably from metal tubing, where the wall is preferably lessthan 1/32 inch in thickness.

The air flow limiter of the invention functions equally well with avacuum pump drawing air through air flow limiter 30 etc. from bottom totop by application of vacuum to outlet end 56 as depicted generally inFIGS. 1 and 2, or by air being supplied under positive pressure at inletend 54 for passage upwardly through air flow limiter 30 etc.

In the claims appended hereto, the term “comprising” is to be understoodas meaning “including, but not limited to” while the phrase “consistingof” should be understood to mean “having only and no more”.

The following is claimed:
 1. An air flow limiter, comprising: a. avertically oriented tube; b. a pair of open-ended telescoping tubularsegments within the tube, an outer tubular segment being fixed and theother open-ended telescoping tubular segment being slideably movablealong the fixed segment in the axial direction; c. a plate extendingpartially across the interior of the vertically oriented tube,positioned for contacting the movable one of the telescoping tubularsegments to limit travel of the moveable telescoping tubular segment,the plate covering an open upper end of the movable telescoping tubularsegment upon contact therewith; d. an actuator connected to the platefor selectably limiting travel of said moveable tubular segment; e. asail positioned in the vertically oriented tube below the telescopingsegments; f. a strut connecting the sail and the moveable telescopingtubular segment; the movable telescoping tubular segment movingvertically within the tube unitarily with the sail responsive to upwardair flow through the tube against the sail.
 2. The adjustable air flowlimiter of claim 1 wherein the moveable tubular segment is moveablebetween a first position at which the moveable segment rests on thefixed segment and a second position which the moveable segment contactsthe actuator.
 3. The adjustable air flow limiter of claim 1 wherein thesurface of the plate contacted by the movable tubular segment is planar.4. The adjustable air flow limiter of claim 2 wherein the portion of themoveable tubular segment contacting the plate surface is annular.
 5. Theadjustable air flow limiter of claim 1 wherein a surface of the platecontacted by the movable tubular segment is flat, the tubular segmentsare cylindrical, and a circular edge of the tubular segment contactingthe plate surface is annular and normal to the axis of the tubularsegment.
 6. The adjustable air flow limiter of claim 1 wherein theactuator is a solenoid.
 7. The adjustable air flow limiter of claim 1wherein the moveable segment contacts a piston portion of the solenoidat one extreme of moveable segment travel.
 8. An adjustable method forlimiting air flow, comprising: a. providing a tube; b. providing withinthe tube a stationary baffle having a cylindrical outlet; c. positioninga movable sail assembly including a sail within the tube; d. providing atelescoping cylindrical member as a part of the assembly; e. permittingthe cylindrical member of the sail assembly to move telescopingly withinthe baffle cylindrical outlet; f. positioning a moveable stop within thetube; g. moving the stop to a selected position corresponding to adesired maximum air flow through the tube; and h. permitting the sailassembly to move responsively to air flow through the tube between aposition at which air flows around the sail assembly and through thetube and a position at which the sail assembly contacts the stop.